B&H and Adorama both list used equipment, but with the new price of a 50mm f1.8 at sixty bucks why would you want a used one? They are plastic and not of the best build quality. Mine sounds like a toy when it is achieving focus but it is the fastest lens that I own and I use it alot . I would not advise a used purchase. I have lenses that I am looking to upgrade as I'm sure do many who frequent this site but Steve has asked that we don't use these forums to list such items and I respect that. It could certainly cause potential problems. Perhaps someone else knows of a site where equipment is listed for resale.